Method of controlling pests in stored goods

ABSTRACT

The invention concerns a method for pest control in stored wares, especially tobacco products, which is characterized by the intermittent microwave treatment of potentially infested stored goods, whereby the duration of treatment and the mean output of the microwaves are so harmonized that the pest itself as well as its eggs are killed. The present invention therefore makes it possible to conduct effective and sustained pest control on infested goods since, in addition to beetles and larvae, the eggs of the pest are eliminated as well, and consequently the development of eggs to the larval stage at a later point in time is prevented. Secondly, using the invention&#39;s method, it is possible to dispense with highly toxic chemicals that can leave residues on the treated commodities and consequently represent a health hazard to anyone consuming the product in question. Due to the possibility of dispensing with highly toxic chemicals, the method is also very economical, as time-consuming and cost-intensive safety measures become superfluous.

[0001] The present invention concerns a method for controlling pests in stored products. Dry plant substances, among them tobacco products, tea, rice, cacao, spices, drugs and dried fruit in particular are considered stored products.

[0002] The problem of infestation with storage pests arises with the above-mentioned commodities. The biscuit weevil (Stegobium paniceum) and the so-called cigarette beetle (Lasioderma serricorne), for example, belong to this category of storage pests. Moreover, these storage pests attack tobacco products in particular, whereby they develop in fermented tobacco or in the finished product. The larvae eat passages into the commodities and pupate on the leaf ribs. This is a problem associated with cigar manufacturing, which consequentially entails considerable economic damages. In general, packaging material offers little protection against storage pests as the larvae penetrate even the smallest cracks and infest the commodity in question. In addition to the economic loss for products that have become unusable, the threatened loss of customer confidence resulting from the purchase of pest-infested wares is considerable.

[0003] One therefore seeks to exterminate the pests. In order to accomplish this, stored commodities are usually fumigated with fumigation agents. Fumigation agents are highly toxic substances such as, hydrocyanic acid; hydrogen phosphides; zinc, calcium, aluminum phosphides; methyl bromide; formaldehyde or ethylene oxide. The infested wares are fumigated with these highly toxic gases, resulting in the death of the beetles and larvae in particular. The advantage of these fumigation agents is their high penetration capacity that not only acts on the surface, but also kills off pests in the interior of the commodity. Nonetheless, this entails the considerable disadvantage that the treated infested commodity retains residues of the fumigation agent, which does not lie just on the surface and therefore cannot simply be washed off. The residues represent a health problem for the user. This is especially the case with tobacco products since these toxic substances are absorbed through the oral mucosa and, as a consequence of inhalation, through the lung surface into the body. Customary fumigation processes present a hazard since it is not only the raw commodity that is fumigated before processing, but the processed commodity, as well, which is thereafter used by the consumer. With tobacco products such as the cigar, not only is the fermented tobacco fumigated, but also the finished cigar. Moreover, large amounts of highly toxic gases are used in this final fumigation step to guarantee that the finished product is pest-free and that the user is not receiving damaged goods. Nonetheless, residues of highly toxic gases remain in the finished product.

[0004] In addition to the stress on the consumer's health, the customary method for pest control entails the disadvantage that in addition to the beetles, only the already ecloded larvae are normally exterminated and often the eggs do not die as a result of the fumigation. Therefore, the danger remains that larvae that survive the fumigation will eclode out of the eggs into the finished product and spoil the latter, which once again results in the undesirable damage to the commodity mentioned above and, as a consequence, the possible loss of consumer confidence.

[0005] The usual method also has the particular disadvantage that safety precautions must be adhered to in handling fumigation agents and in dealing with hydrogen phosphide and hydrocyanic acid in order to avoid endangering the workers, as these substances are not only highly toxic, but can also form explosive mixtures. Strict safety conditions must therefore be complied with in storing the fumigation agents and in handling them, which entails increased costs in addition to the heightened danger to the working personnel and the necessary circumspection resulting therefrom. In accordance with the Hazardous Substances Act and the relevant technical regulations, owing to their hazardous nature, such fumigation agents may only be issued to companies having a permit for these substances, where only holders of certificates of qualification or experts use them.

[0006] Moreover, fumigation is inherently very expensive. Fumigation basically includes five operations that can entail from days to months depending upon the size of the object to be fumigated. Moreover, in any given case, gas concentration measurements are to be conducted when introducing the fumigation agent, in monitoring the fumigation, in connection with ventilation and during approval operations. In addition, the objects treated with the chemical agents can only be approved when certain concentration values are exceeded. This results in an inability to plan precisely for fumigation time periods and to the occurrence of delivery difficulties under certain circumstances. Suitable storage facilities must be made available for the commodities until they have exceeded the allowed concentration in each case.

[0007] Overall, there is an immense amount of time and expense associated with customary fumigation methods, which has a disadvantageous effect on the productivity of a processing facility. In addition, these agents represent a considerable health risk for workers and the consumer. The strain on the environment caused by highly toxic chemicals is also extraordinarily disadvantageous; some of these, such as bromomethane, also harm the ozone layer.

[0008] A further method for combating storage pests, which owing to its risks may only be used in certain countries, uses gamma rays in order to deal with the pests. Even in this connection, the health risks are considerable for workers as well as for the consumer since the formation of carcinogenic radicals can occur in the commodity in addition to the high radiation stress.

[0009] Therefore, underlying the invention is the objective of readying a method for controlling pests in stored commodities that is simple to implement and which improve the state of the art so that no substances having a negative affect on health are used in effective pest control.

[0010] The invention accomplishes the objective by treating the wares, at least intermittently, with microwaves, whereby the duration of treatment and the mean output of the microwaves are harmonized with each other so that the pest itself, as well as its eggs, are exterminated.

[0011] With the invention's method, the disadvantages associated with the state of the art method are surprisingly avoided. Thus the present invention makes it possible to dispense with the fumigation or gamma ray treatment usually used for pest control. In this way, the aforementioned disadvantages of these treatments are advantageously avoided.

[0012] The invention's use of microwaves for the effective elimination of the pest and its eggs is harmless for the end user as well as for the workers participating in the manufacture of the respective product. When using the invention's method, no hazardous residues resulting from the use of chemicals remain in the product and the user can be sure that he/she is not ingesting any health-endangering substance of this type with the product. The highly toxic chemicals used for these treatments are eliminated, which is advantageous for occupational safety. The costly and expensive safety precautions for handling and storing the highly toxic chemicals normally used can be eliminated. The invention's method is therefore conducive to cost savings. In addition, fewer operations are necessary, which increases productivity. In addition to the advantage in saving of steps, it should also be considered that the commodity can be further processed immediately and need not be stored until certain concentrations in toxic substances have been exceeded. Consequently, the product's subsequent processing can be planned in advance without the uncertainty parameters inherent in the traditional fumigation method.

[0013] In addition to the advantage of cost savings based on the elimination of superfluous safety precautions and unnecessary storage facilities, the invention's method is basically more environmentally friendly than the traditional techniques, as no environmentally stressful chemicals or radiation are used. Moreover, with the invention's method, potential chemical elimination is advantageous for the generally desired reduction of chemical use in pest control vis-á-vis detrimental environmental stresses. Dispensing with chemicals is also extraordinarily beneficial since the user is saved from unnecessary health risks owing to toxic chemicals. This is of great economic advantage in the face of increasing critical consumer consciousness regarding substances of this type, as dispensing with hazardous chemicals can be used in advertising to good effect.

[0014] With the invention's method, the duration of treatment and the mean output of the microwaves used are harmonized with each other in such a way that the storage pest itself is killed, as well as its eggs. The beetles, as well as its larva, are understood to be pests that cause damage to the stored commodity by digging passages. With the invention's method, not only the is the pest eliminated, but also its eggs, which are often resistant to conventional fumigation methods. Since the eggs are killed off, it is assured that no larvae will eclode from surviving eggs during transport and/or storage of the product, resulting in a damaged commodity. The danger of economic damage caused by pests is therefore minimized by the invention's method, as the commodity is pest-free over the long term because the eggs have been killed. Higher quality standards can be guaranteed to the dealer and the customer.

[0015] Furthermore, it is possible to vary the microwave treatment's duration and intensity so that they can be advantageously adapted for different pests infesting the stored goods in question and the pests can consequently be effectively exterminated. It is thus possible to control the process so that the mean output of microwave radiation and the duration of the treatment are harmonized so that the pests are effectively killed while the stored goods remain undamaged. The various properties and sensitivities of different stored wares in relation both to irradiation intensities and irradiation duration can thus be taken into consideration. Therefore, the most varied of infested commodities that are conventionally fumigated or irradiated can be treated effectively and in an environmentally friendly way using the invention's method.

[0016] The invention's use of microwaves for pest control is therefore also advantageous insofar as the process can be conducted in such a way that the product is not harmed and no residues from the treatment remain on the commodity. Thus the use of microwaves has the advantage of a relatively short treatment time for effective material processing to eliminate pests as the use of microwaves effects an advantageous focusing of energy. Microwave processing results in denaturing of the proteins in the cells of the pest, which consequently kills the pest in all its developmental stages. Protracted heating phases that can damage the stored commodity in question due to the protracted, constant high temperatures can be dispensed with. Using the invention's method, it is possible to heat commodity uniformly, and contact heating that can scorch the commodity, a possibility when using a hot plate, for example, can be eliminated. In this way, the product is not dried out, which is especially disadvantageous in tobacco manufacture. Traces of processes, as, for example, scorched places on the commodity, are also avoided, which is conducive to an attractive appearance.

[0017] In accordance with an advantageous further development of the present invention, the potentially infested ware is processed with microwaves but for a short time. Thus the duration of the microwave action preferably lies below one minute at ca. 200-1200 W, preferably at 700 W. Moreover, the duration of treatment can also to be adapted to the size of commodity in question. Conducting microwave treatment for a short period of time also spares the stored good. In this way, defects in the product are avoided and the commodity's taste, aroma, appearance remain uninfluenced by the irradiation. In order to irradiate larger quantitative units effectively, they can be conveyed through the irradiation area proper.

[0018] For processing tobacco used in cigar manufacture, a treatment duration of 10 to 15 seconds at ca. 700 W has proven sufficient to the extent that small quantitative units, such as, a cigar box, were being irradiated. This short treatment duration of a few seconds leads moreover to effective elimination of cigarette beetle eggs and larvae, but has no disadvantageous repercussions on the quality of the tobacco product. The short treatment periods also have the advantage that effective and continuous pest control requires little time in the production of the finished product. Through the advantageous time savings, a manufacturing facility's production capacity, e.g., for cigars, can be increased significantly since pest control will no longer consume long periods of time ranging from several days to months.

[0019] With advantageous further development of the present invention, it is further proposed to adapt the microwave frequency for the necessary penetration depth of the microwaves into the commodity. Microwave frequencies are used here in a range from ca. 2 to 20 GHz, preferably 2 to 5 GHz. In this way, the irradiation can be adapted to the stored commodity in question, as well as to the configuration of the stored ware. Thus, irradiation duration and intensity are adapted to the pest to be killed, on the one hand, and the microwave frequency can be adapted to the necessary penetration depth of the microwaves on the other. These can be adapted to the condition of the of the respective commodity and also to its configuration. In the present case, it is possible to decide whether the tobacco should be irradiated in leaf form or in cut form, or whether the finished cigar itself should be irradiated.

[0020] It is further proposed in further development of the present invention that at least one sensor be used that continuously measures the temperature and/or acting radiation, whereby the processing temperatures and/or irradiation intensities are automatically adapted to reference values that can be specified in the data memory. These can be entered, for example, into the control unit's data memory. During irradiation, the sensor measures the relevant conditions of the infested wares and transmits these to the control unit, which automatically conducts a comparison with the actual value measured by the sensor and the reference values specified in the data memory as standard values and adapts the irradiation conditions so that the actual values basically correspond to the standard values. In this way, it is guaranteed that for one, the parameters necessary for killing the pests are complied with and secondly, no limiting values are exceeded, whereby an excess could possibly lead to commodity damage. The goods can also be shaken by means of motion devices or subjected to swirling motion in order to assure that the product is optimally irradiated. Controlling the duration of treatment is also possible. It is possible to check the conditions acting on the product exactly and to assure the appropriate processing of the product with effective pest extermination. A type of monitoring function is introduced which prevents excessively long or excessively intensive irradiation and consequent damage to the respective goods.

[0021] In accordance with a further proposal, pest control can take place either before and/or during processing of the stored goods or in the finished product itself. It is also conceivable that with certain commodities or storage pests, microwave processing is conducted for the sake of safety during processing as well as on the finished product in order to rule out pest infestation in the completed product. When producing tobacco products, it is possible to irradiate fermented tobacco and/or the finished product, for example, a cigar, with microwaves. Processing the finished product with microwaves simply and advantageously eliminates the final fumigation step in which large amounts of highly toxic fumigation agents are used in the traditional method. The invention's method is especially suited to avoiding this final fumigation step in which residues of the toxic fumigation agents can remain on the commodity, and to dispensing with highly toxic fumigation agents. Processing the completed product according to the invention's method is simple, and existing operations can be adapted without great expense so that it is possible to save the final fumigation operation, representing a considerable advantage in relation to the customary method and an advantage to the consumer as the finished commodity is less chemically burdened.

[0022] In accordance with further advantageous refinement of the present invention, it is furthermore proposed to shock freeze the stored wares subsequent to microwave processing below the freezing temperature. Here the goods are shock-frozen at −10° C. to ca. −40° C., preferably at −25° C. In these temperature ranges, cold results in effective elimination of the pest. It results in freezing the fluid cytosol in the cells of the pest, whereby ice crystals form and the latter die out. This treatment is therefore advantageous to pest control. It can be used as an additional safety measure to guarantee that the product is and remains pest-free. Furthermore, cold treatment conserves the moisture, taste and aroma of the stored commodity in question. This method is especially beneficial when processing takes place on the finished product according to the invention's method. The finished goods are cooled directly by shock freezing and can also be transported or stored in this state. In addition to killing the pest in all of its developmental stages, storage in this state has the advantage of maintaining a constant moisture content in tobacco products and dehydration is avoided. Re-infestation of the product at these temperatures is eliminated during transport or storage.

[0023] With advantageous further development, it is proposed that the duration and temperature of shock freezing be harmonized and that the parameters be adapted to the stored commodity in question. In this way, it is possible to adapt the duration of cooling of the stored ware to be treated in any given case so that damage to the latter is avoided.

[0024] In accordance with a further proposal, shock freezing takes place for a period from ca. 24 h to 72 h. The storage pests are effectively exterminated within this time span, making shock freezing an adequate measure in combination with microwave treatment.

[0025] The present invention will be explained below on the basis of an embodiment. This serves exclusively for more detailed explanation and is not restrictive. Here the present example relates to the use of the invention's method for controlling the cigarette beetle in tobacco in connection with the manufacture of cigars. Moreover, the finished cigar is treated against pests.

[0026] The cigars potentially infested with pests are irradiated with microwaves subsequent to their manufacture in order to kill off the beetles, larvae and eggs of the storage pest, in the present example the cigarette beetle (Lasioderma serricorne). Various parameters are taken into consideration in irradiating the cigars. Thus the duration of treatment and the mean output of the microwaves are harmonized so that that they not only kill the pest and its eggs, but also leave the tobacco product unaffected. Moreover, these parameters can be selected and adjusted prior to treatment. The amount to be irradiated is also to be considered in any given case. Relevant data such as permissible irradiation duration, intensity, temperature and so forth are specified as reference values in the control unit's data memory. Irradiation is only conducted for a period of ca. 15 to 20 seconds at 600 W to 900 W, preferably at 700 W. The brevity of the irradiation process is in itself beneficial to the tobacco. This prevents excessive dehydration of the tobacco.

[0027] Subsequent to irradiation, the finished cigar is shock frozen for ca. 72 h at approximately −25° C. This shock freezing serves as an additional storage pest control measure. The cigar can be transported in this condition, so no additional storage facilities are necessary for the cooled cigars. Later, the cigars are slowly thawed. The cigar thus processed is distinguished by an aroma which is in no way impaired by treatment and furthermore has no residues from pest control chemicals, a benefit to the health of the consumer.

[0028] The invention's method has wide-reaching application possibilities for pest control. Moreover, it has proven itself for controlling the cigarette beetle (Lasioderma serricorne) that infests the greatest variety of stored goods such as tobacco products, spices, drugs and dry fruit. Its use in connection with tobacco has proven very effective. Above and beyond these applications, the invention's method can also be used for other stored goods and against other storage pests. Owing to the low costs and expenditure of effort in controlling pests, time as well as money can be saved with the invention's method, and the pests are exterminated more effectively and with a method that is more environmentally friendly than with traditional methods. This benefits the consumer since the products are left unchanged, and no health-impairing chemical residues remain on the products. 

1. Method for pest control in stored wares, especially tobacco products, characterized by processing potentially infested stored commodities with intermittent microwaves, whereby the duration of treatment and the mean output of the microwaves are harmonized so that the pest itself as well as its eggs are killed:
 2. Method according to claim 1, characterized by processing infested goods for a period of time under 1 minute with microwaves at ca. 200 W to 1200 W, preferably at 700 W, whereby these parameters are adapted to the amount of infested wares to be irradiated in any given case.
 3. Method according to one of claims 1 or 2, characterized by irradiation of potentially infested tobacco products with microwaves for 10 to 15 sec.
 4. Method according to one or more of claims 1 to 3, characterized by adapting the employed microwave frequency to the requisite microwave penetration depth into the commodity, whereby microwave frequencies are used in a range from 2 to 20 GHz, preferably 2 to 5 GHz.
 5. Method according to one of claims 1 to 4, characterized by continuously measuring the temperature and/or radiation acting on the commodity with at least one sensor, whereby the treatment temperature and/or radiation intensities are automatically adapted to reference values that can be specified in a data memory.
 6. Method according to one or more of claims 1 to 5, characterized by harmonizing the duration of treatment, temperature and mean output of the microwaves so that the pest itself as well as its eggs are killed off, but the stored goods are not damaged.
 7. Method according to one or more of claims 1 to 6, characterized by the fact that pest control takes place before and/or during processing of the raw commodity.
 8. Method according to one or more of claims 1 to 6, characterized by the fact that pest control takes place in the finished product.
 9. Method according to one or more of claims 1 to 8, characterized by shock freezing the stored goods subsequent to microwave processing at a minimum of −10° C. to −40° C., preferably at −25° C.
 10. Method according to one or more of claims 1 to 9, characterized by harmonizing the duration and temperature of the shock freezing and adaptation to the respective stored commodity.
 11. Method according to one or more of claims 1 to 10, characterized by shock freezing for a period of time up to 72 h. 